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Date: Fri, 6 Oct 2017 13:04:35 +0100 From: Roman Gushchin <guro@...com> To: Michal Hocko <mhocko@...nel.org> CC: <linux-mm@...ck.org>, Vladimir Davydov <vdavydov.dev@...il.com>, Johannes Weiner <hannes@...xchg.org>, Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>, David Rientjes <rientjes@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Tejun Heo <tj@...nel.org>, <kernel-team@...com>, <cgroups@...r.kernel.org>, <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org> Subject: Re: [v11 4/6] mm, oom: introduce memory.oom_group On Thu, Oct 05, 2017 at 04:31:04PM +0200, Michal Hocko wrote: > Btw. here is how I would do the recursive oom badness. The diff is not > the nicest one because there is some code moving but the resulting code > is smaller and imho easier to grasp. Only compile tested though Thanks! I'm not against this approach, and maybe it can lead to a better code, but the version you sent is just not there yet. There are some problems with it: 1) If there are nested cgroups with oom_group set, you will calculate a badness multiple times, and rely on the fact, that top memcg will become the largest score. It can be optimized, of course, but it's additional code. 2) cgroup_has_tasks() probably requires additional locking. Maybe it's ok to read nr_populated_csets without explicit locking, but it's not obvious for me. 3) Returning -1 from memcg_oom_badness() if eligible is equal to 0 is suspicious. Right now your version has exactly the same amount of code (skipping comments). I assume, this approach just requires some additional thinking/rework. Anyway, thank you for sharing this! > --- > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index 085056e562b1..9cdba4682198 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -122,6 +122,11 @@ void cgroup_free(struct task_struct *p); > int cgroup_init_early(void); > int cgroup_init(void); > > +static bool cgroup_has_tasks(struct cgroup *cgrp) > +{ > + return cgrp->nr_populated_csets; > +} > + > /* > * Iteration helpers and macros. > */ > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c > index 8dacf73ad57e..a2dd7e3ffe23 100644 > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -319,11 +319,6 @@ static void cgroup_idr_remove(struct idr *idr, int id) > spin_unlock_bh(&cgroup_idr_lock); > } > > -static bool cgroup_has_tasks(struct cgroup *cgrp) > -{ > - return cgrp->nr_populated_csets; > -} > - > bool cgroup_is_threaded(struct cgroup *cgrp) > { > return cgrp->dom_cgrp != cgrp;
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